Cataracts are a lens disorder resulting from the further progression of protein coagulation and calcification. There are four common types of cataracts: senile cataracts associated with aging and oxidative stress, traumatic cataracts which develop after a foreign body enters the lens capsule or following intense exposure to ionizing radiation or infrared rays, complicated cataracts which are secondary to diseases such as diabetes mellitus or eye disorders such as detached retinas, glaucoma and retinitis pigmentosa, and toxic cataracts resulting from medical or chemical toxicity. Regardless of the cause, the disease results in impaired vision and may lead to blindness.
Treatment of such severe lens diseases requires surgical removal of the lens from the capsular bag. The surgical procedure typically involves phacoemulsification, followed by irrigation and aspiration. Implantation of an intraocular lens (IOL) following the extraction of a cataract is now a standard ophthalmic procedure. Current IOLs include rigid, non-deformable lenses as well as rollable or foldable lenses. Furthermore, techniques have been suggested wherein a low viscosity lens material is directly injected into the empty capsular bag and cured in situ as part of the surgical procedure to form an IOL, reducing surgical incisions to about 1 mm. In such a process the capsular bag is used as a mold to form the shape of the lens and thereby contribute to control its refraction.
PCO is the most common postoperative complication of cataract surgery, occurring in 20% to 40% of patients. PCO is a disease caused by epithelial cells in the lens equatorial zone that are not removed during cataract surgery because of their strong adhesion to the matrix components of the lens capsule. Following cataract surgery these epithelial cells migrate onto and across the posterior capsule, eventually populating its entire surface. At a time in the development of PCO not yet specified, these cells lose their epithelial phenotype and become mesenchymal like, a process known as EMT. EMT is characterized the expression of proteins such as α-smooth muscle actin (α-SMA) and fibronectin. α-SMA, a muscle specific cytoskeletal protein, confers these mesenchymal cells with contractile function. The wrinkling of the posterior capsule that occurs in PCO is likely caused by contraction of the epithelial cells following their acquisition of a mesenchymal phenotype. Wrinkling of the capsule is thought to be responsible for the light scattering that causes impaired vision in PCO. Patients with PCO are treated with laser surgery, neodynium:YAG laser posterior capsulotomy, which creates an opening in the opacified posterior capsule and lets light pass through. While this restores vision, it places patients at higher risk for further visual impairment. In addition, the medical costs associated with this procedure are among the highest in the United States.
Accordingly, there is a great need for methods preventing PCO.